A fluorine-containing resin has been and is widely used in many fields due to its remarkable excellence in heat resistance, mechanical properties, chemical resistance and weatherability. The use of it includes a use as a coating-forming component in a coating composition. For example, there is known a fluorine resin coating composition containing a tetrafluoroethylene polymer or a vinylidene fluoride polymer, which is used in the fields of chemical industry, foods, construction and machinery due to its excellence in lubricity, nontackiness, weatherability and chemical resistance.
The defect with the above fluorine resin coating composition is that it is required to be baked at a high temperature and the range of its use is inevitably limited. In recent years, therefore, it has been attempted to develop a fluorine-based, solvent-type coating composition which contains, as a main component, a fluorine-containing resin soluble in an organic solvent and containing a reactive group curable at room temperature.
Meanwhile, as fluorine-containing resins soluble in an organic solvent, there are known copolymers obtained from fluoroolefins and vinyl monomers copolymerizable therewith, as disclosed in JP-A-61-275311, JP-A-61-57690, JP-A-62-174213, JP-A-63-182312, U.S. Pat. No. 4,960,827, U.S. Pat. No. 4,859,755, U.S. Pat. No. 4,690,968, U.S. Pat. No. 4,436,773, U.S. Pat. No. 4,436,772, U.S. Pat. No. 4,345,057, U.S. Pat. No. 3,218,287, U.S. Pat. No. 3,166,524, U.S. Pat. No. 2,834,767 and EP-A-328,157.
In the above copolymers, however, alkyl vinyl ethers or special vinyl carboxylates are used as a comonomer, and these comonomers, which provide a coating with flexibility, are insufficient with respect to coating hardness, coating gloss, adhesion of a coating to a substrate, pot life, drying properties of a coating, compatibility with a curing agent or a solvent for a fluorine-containing resin, pigment dispersibility and storage stability. Thus, a fluorine-containing resin having well-balanced properties among these properties has not yet been developed.